/*
 * Copyright 2012-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cn.springcloud.gray.bean.convert;

import java.util.EnumSet;
import java.util.Set;

import org.springframework.core.convert.converter.Converter;
import org.springframework.core.convert.converter.ConverterFactory;
import org.springframework.util.Assert;

/**
 * Converts from a String to a {@link java.lang.Enum} by calling searching matching enum
 * names (ignoring case).
 *
 * @author Phillip Webb
 */
@SuppressWarnings({"unchecked", "rawtypes"})
final class StringToEnumIgnoringCaseConverterFactory
        implements ConverterFactory<String, Enum> {

    @Override
    public <T extends Enum> Converter<String, T> getConverter(Class<T> targetType) {
        Class<?> enumType = targetType;
        while (enumType != null && !enumType.isEnum()) {
            enumType = enumType.getSuperclass();
        }
        Assert.notNull(enumType, "The target type " + targetType.getName()
                + " does not refer to an enum");
        return new StringToEnum(enumType);
    }

    private class StringToEnum<T extends Enum> implements Converter<String, T> {

        private final Class<T> enumType;

        StringToEnum(Class<T> enumType) {
            this.enumType = enumType;
        }

        @Override
        public T convert(String source) {
            if (source.isEmpty()) {
                return null;
            }
            source = source.trim();
            try {
                return (T) Enum.valueOf(this.enumType, source);
            } catch (Exception ex) {
                return findEnum(source);
            }
        }

        private T findEnum(String source) {
            String name = getLettersAndDigits(source);
            for (T candidate : (Set<T>) EnumSet.allOf(this.enumType)) {
                if (getLettersAndDigits(candidate.name()).equals(name)) {
                    return candidate;
                }
            }
            throw new IllegalArgumentException("No enum constant "
                    + this.enumType.getCanonicalName() + "." + source);
        }

        private String getLettersAndDigits(String name) {
            StringBuilder canonicalName = new StringBuilder(name.length());
            name.chars().map((c) -> (char) c).filter(Character::isLetterOrDigit)
                    .map(Character::toLowerCase).forEach(canonicalName::append);
            return canonicalName.toString();
        }

    }

}
